Certainly one of the worst examples.
The Sultan is perhaps one of the most prolific examples, but specifically Rolls-Royce and Bentley have never really stopped doing coach built offerings, and while you do need to be as rich as a dictatorial head of state in order to afford the most bespoke of commissions lesser examples are not unknown, cars like the Bentley P116 and David Beckham's factory personalised Bentleys are products of the same system that built cars like the Java, Dominator, Buccaneer and Silverstone for the Sultan, or some of the British Royal family's cars.
There seems to be a fairly long list of bespoke Ferrari's for the Sultan, but also a number of more recent offerings also just for quite rich people, the SP4 EC for Eric Clapton, for example, and Aston Martin who've also done a number of special vehicles for the Sultan are still doing things like the Victor. McLaren's special vehicles division, again has done things for the Sultan, but has also demonstrated their competence at bespoke products such as the X-1... there are likely many more examples that I can't recall, and many more that just aren't known about. (edit: TheSC18 and SC20 from Lamborghini I think are one-offs not sure if they're bespoke commissions or not)
In fairness Rolls-Royces ability to do it in house seemed to have been lost when BMW took them over, with Mulliner Park Ward switching from traditionally being a Rolls-Royce entity, to a Bentley controlled brand name, so this recent resurgence from them is good to see. Previously we saw the Rolls-Royce Hyperion, but this was executed by Pininfarina, rather than Rolls-Royce themselves.
I think the extreme prices being seen could simply be a reflection of current times, but you have to keep in mind that these are cars developed with manufacturer overheads... independent coachbuilders, dare I say - the aftermarket - may be able to turn out similar stuff, but it's never going to be at the same cost or price as getting the OEM to do it. The Bugatti Voiture-Noire is an interesting halfway point, built as a one-off, somewhat to customer specifications, but a car they already knew they wanted to build, and that was somewhere between 10 and 20 million Euros, so I'd suggest again, that the price is as much about cost ammortisation as anything.
